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Tags reveal if frozen food is rotten

By Andy Coghlan

A simple plastic disc designed to sit inside food packaging changes colour when exposed to the noxious vapours given off by rotting food. Its developers hope it will provide a simple way for consumers to tell whether food has gone off.

Dwight Miller and his colleagues at the US National Center for Toxicological Research in Jefferson, Arkansas, created the polymer discs. They contain complex organic dyes that change colour drastically from clear to telltale pink, blue or yellow, depending on the type of food. Reference colours printed on the packaging will let people judge if food has gone bad.

The first disc Miller hopes to see launched is an indicator for frozen fish and shrimps. The organic dye for this tag is similar to one used to make bubblegum pink. It reacts with the stinking vapours of trimethylamine, dimethylamine and ammonia produced by rotting fish. The same test should work with beef and lamb. It already works with stale elk meat, Miller says.

Frozen vegetables are next, thanks to a disc that detects formic, acetic and other acids, which are formed when vegetables decay.

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“Some sort of user-friendly device would be ideal for the home,” says Tim Brocklehurst, head of microbial biophysics at the Institute of Food Research in Norwich.

But while the tags could be available within two years, Miller warns that supermarkets may not be too keen to adopt them if it means they end up throwing away more spoiled food than they normally would.